1. Field of the Invention
The present invention relates to an improvement of a multiple electron beam type picture image display apparatus and especially concerns the picture image display apparatus having a novel structure enabling easy manufacture and high quality picture display.
2. Description of the Prior Art
Several proposals have been made on multiple electron beam type flat shaped picture display device, for example in the U.S. Pat. No. 3,935,500 (to Oess et al.) and SID 78 Digest pp. 122 to 127. Furthermore, three of the inventors of the present invention have invented and proposed a multiple electron beam type picture display apparatus described in the specification of the Japanese Patent Application Sho 53-106788 filed on Aug. 30, 1978 (published as unexamined patent gazette Sho 55-33734 on Mar. 10, 1980) and also described in the specification of the U.S. Pat. No. 4,227,117 (to Watanabe et al.) patented on Oct. 7, 1980.
The structure of picture image display apparatus of the abovementioned described invention is shown in FIG. 1(a) which is an exploded view of the principal part of the apparatus. The apparatus comprises, as shown from the upper part to the lower part in FIG. 1(a), and FIG. 1(b), an isolation electrode 2 having a plural number of isolation walls 201 to define oblong isolated spaces 202, a row of predetermined number M (e.g. M=48) of linear thermionic cathodes 1 disposed in parallel (i.e., line cathodes, each of which comprises a linear filament line to be heated by a low voltage, e.g., D.C. 10 V and electron emissive oxide coating thereon, and hereinafter is referred to as linear thermionic cathode) each being disposed in the isolated spaces 202, an extractor being disposed in the isolated spaces 202, an extractor electrode 3 having a predetermined number N (e.g. N=107) of electron beam passing apertures 3a disposed in rows under the linear thermionic cathodes 1, a row of control electrodes 4 for controlling beam intensity disposed parallelly in parallel in a direction perpendicular to those of said linear thermionic cathodes 1 each having electron beam passing openings 4a under the apertures 3a, an electron beam forming electrode 5 having electron beam passing openings 5a under the openings 4a, a row of vertical deflection electrodes comprising pairs of common-connected first electrodes 6 and common-connected second electrodes 6', a row of horizontal deflection electrodes comprising pairs of common-connected first electrodes 7 and common-connected second electrodes 7', an electric field shielding electrode 8, an anode 9 of vapor-deposited thin aluminum film, and a phosphor screen 10 formed on a face panel 11 of a vacuum enclosure. Every electron beam e, e . . . passes through deflection spaces 62, 62 . . . and 72, 72 . . . defined by the deflection electrodes pairs 6, 6', . . . and 7, 7', . . . disposed regularly in the same order with respect to every electron beam as shown in FIG. 1(a) and FIG. 1(b).
In the operation of such multiple electron beam type display apparatus described in the abovementioned specifications, scannings of beam spots on the phosphor screen are made in the known line-at-a-time type scanning, wherein ordinary time-sequential image signal is converted into a plural number of parallel signals. For example, by taking a case to display an image field raster having numbers of picture elements of 240 (in vertical direction) times 321 (in horizontal direction), with regard to the horizontal scanning of the beam spots the raster is divided into a plural number N of vertically oblong sections, wherein the horizontal scannings are carried out simultaneously in all of N sections. Then, each section has picture elements of n=(321/N) in the horizontal direction. For example, when the number N of the vertical sections is 107, the number n of picture element in each section is 3. For such example, 107 beam spots are produced from each linear thermionic cathode and 107 control electrodes are provided in order to control the 107 electron beam intensities. In the apparatus, the horizontal scanning is made by using saw-tooth wave having a horizontal scanning period H applied to the horizontal deflection electrode and in a manner that all the N beam spots are deflected simultaneously to scan in the same direction taking one horizontal scanning period H. The horizontal scanning period H is equal to the horizontal scanning period of the ordinary time sequential television signal. In order for attaining such line-at-a-time-scanning, the ordinary time sequential image signal is preliminarily converted into the N parallel signals of the line-at-a-time type.
The vertical scanning of the described apparatus is made by dividing the raster into a plural number M of horizontally oblong sections, and at first in the first section, for example in the uppermost section, the plural number of beam spots, which simultaneously scan, also scan vertically (downwards). When the vertical scanning in the first section is over and all the beam spots reach the bottoms of the first horizontally oblong sections, then the forming of electron beams from the electron from the first linear thermionic cathode ends and the forming of electron beams from the electrons from the second linear thermionic cathode starts, and the vertical scannings of the beam spots start in the second horizontally oblong section and scan downwards in the same way as in the first section. The vertical scanning is made thus downwards to the bottom or M-th section by applying a saw-tooth wave having a period (V/M), where V is the vertical scanning period of the ordinary television signal. For the abovementioned example of the raster having the number of vertical picture element of 240, when the number M of the horizontally oblong sections is 48, each of the section has the horizontal scanning lines of a number of m=(240/48)=5. That is to say, the example apparatus uses 48 linear thermionic cathodes, and each cathode vertically scans to produce 5 horizontal scanning lines.
FIG. 2 shows a block diagram of an example of the circuit for driving the abovementioned apparatus described in the abovementioned specifications. The circuit of FIG. 2 is constituted as follows. A video signal from the input terminal 12 is led to a video signal amplifier 13 and a synchronization signal separator 14, output of which is given to a sampling pulse generator 15 and a synchronization signal generator 19. A memory circuit 16 receives time sequential signal from the video amplifier 13 and sample-hold it in order for conversion it to the parallel type video signal by a multiplexer circuit 17. That is, the multiplexer circuit 17 takes out memorized video signal from the memory 16 and rearranges it into the N (=107) parallel signals, in each of which n (=3) data in the memory 16 are rearranged into time sequential signal to take the time period of H. The parallel outputs of the multiplexer circuit 17 are given through an amplifier 18 to the control electrodes of the display apparatus. Horizontal deflection signal generator 20 and vertical deflection signal generator 22 receive signal from the synchronization signal generator 19 and issue horizontal deflection signal and vertical deflection signal through the amplifiers 21 and 23 to the horizontal deflection electrodes and vertical deflection electrodes of the display apparatus, respectively. A cathode control circuit 24 receives signal from the synchronization signal generator 19 and issues control signal to the linear thermionic cathodes, in order that electron beams are selectively formed from the electrons from a selected linear thermionic cathodes in sequence by application of negative potential with respect to the electrode 3 thereto, thereby to scan for the period of m.times.H.
FIG. 3 shows waveforms (A), (B), (C), (D), (E), (F) and (G) of various parts of FIG. 2 circuit for the example of n=3 and m=5. The waveforms (A) and (B) are those of horizontal synchronization signal and vertical synchronization signal, wherein H designates the time period of one horizontal scanning and V designates the time period of one vertical scanning of the ordinary television signal. The waveforms (C) and (D) are voltages to be applied to the first and the second linear thermionic cathodes, respectively for switchingly operating the cathode in sequence. The waveforms (E) and (F) are issued from the vertical deflection signal generator circuit 22 and horizontal deflection signal generator circuit 20, respectively, and the waveform (G) is the control signal to be applied to the control electrode 4 of the display apparatus. Accordingly, the scannings of the beam spots seen at enlarged parts of the phosphor screen is as shown in FIG. 11(a).
The structure of the apparatus of FIG. 1(a) has a large number of deflection electrodes, such as 107 common-connected first electrodes 7 and 107 common-connected second electrodes 7', that is 214 deflection electrodes forming a row in total. Therefore, the pitch of the deflection electrodes must be 1 to 2 mm, and hence the width of each one deflection electrode 7 or 7' must be 0.2 to 0.5 mm. Disposing such fine deflection electrode in parallel insulating each-other neighboring ones may make the manufacturing process very difficult, and furthermore such fine wires may make bending or sag during heating and cooling processes, or such fine electrodes likely to form uneven surfaces during etching process to make them. Accordingly, the picture image reproduced on such apparatus is liable to distortions of the deflection.
In order to avoid such disadvantage of the abovementioned very fine deflection electrodes, a use of wide deflection electrodes has been considered, but such wide deflection electrodes have disadvantages of larger deflection distortions and poor resolution. Such disadvantages are elucidated referring to FIG. 4(a) showing an example of deflections by the fine deflection electrodes of the apparatus of FIG. 1, and FIG. 4(b) showing an example of deflections by the wide deflection electrodes. As comparingly shown in FIGS. 4(a) and 4(b) by use of the wide deflection electrodes as in FIG. 4(b) the number of electrodes are largely reduced to less than half and such wide electrodes make the manufacturing easier. However, as shown by FIG. 4(b), the deflection angle becomes much larger in case of the wide deflection electrodes, and such wide angle deflection leads to distortions of deflection, and as shown by the chain lines in FIG. 4(b), the wide angle deflection is likely to induce spreading of the deflected electron beams and hence erroneous impingement on the neighboring phosphors, and may cause decrease of resolution or color saturation.